Dark Sky

The night sky is a universal environmental and cultural resource. Many parks and other natural spaces offer night sky viewing, benefitting humans and animals alike.

NPS photo

 

When was the last time you saw the Milky Way? Have you ever oriented yourself to Polaris, the "North Star"? Have you noticed small songbirds cast their shadows under the light of the full moon?

Your answers rely, in part, on whether you've had access to truly dark skies. Organ Pipe Cactus has some of the darkest skies in the country and has spectacular night sky viewing! Parks and rural places provide an unmatched opportunity to view this nightly phenomenon. Away from the fuzzy glow of cities, the night sky provides a velvet backdrop for natural light. The fascinating night sky is not only beautiful to witness but is useful for animals and humans alike.

 

Star parties and astronomy programs occur during the winter months at Organ Pipe Cactus.

NPS photo/Kat Connelly

Dark Skies in the Parks

Parks are wonderful places to enjoy the night sky. Over 40 parks are designated "Dark Sky Parks", where preservation of the night sky is paramount. Many parks not on the list still hold opportunities to see constellations, planets, and other celestial bodies. These unique places offer refuge from lights to animals and humans alike.

Here at Organ Pipe Cactus, there are many ways that you can enjoy the night sky. Discover more about the wonders of a natural night sky by visiting the National Park Service's Night Sky website!

 

Exploring the monument at dark is a wonderful way to spot desert animals out and about!

NPS photo

What Happens at Night?

No matter where you are, you can usually tell it is night by stepping outside. Visual and auditory cues likely tell you that it's time to rest. Similarly, when the sun rises, so does the average human. The presence and absense of natural light drives this sleep-wake cycle known as the circadian rhythm. Humans, animals, and even plants and fungi all have circadian rhythms that influence their activity.

Creatures of the Night

For many animals, the sun setting is their cue to become active. Here in the Sonoran Desert, animals like bats and owls, and plants like cacti become more active at night. Night and day bring about different events and behaviors that keeps the ecosystem ticking like clockwork.

Birds Use Dark Skies as a Tool

Many songbirds change their sleep-wake cycle during migration. The shift in seasons bring different lengths of day, letting birds know it is time to fly. This shift lets birds use the position of the moon, the stars, and Earth's magnetic field like a compass.

During migration, birds rely on dark skies and a predictable environment. Birds are able to navigate with incredible precision using environmental cues. However, if birds migrate near human-made or lit structures, they face serious danger.

Lights Can Guide, but Can Also Confuse

Animals and humans expect darkness to come in cycles, and a bright light at night can be very confusing. You have likely seen moths and other insects swarm around lamps at night. These insects are not the only animals to be drawn in.

Individual birds are hard to notice, but they can also follow lamp light and become disoriented. Sometimes, birds will follow lights of vessels onto open water, becoming stranded. Others will find the light source, and circle it until exhausted, never reaching their destination.

 

"Sky glow", a form of light pollution along the horizon, reaches all the way to the monument from Phoenix and Tucson, well over 100 miles away.

NPS photo

A Changing Nightscape

Humans are adapted to sleep at night, and our eyes cannot see well in the dark. As we expanded our schedules to work and live into the night, our lights became more and more powerful. However, as much as 50% of human-made lighting is lost to the environment. This means that up to half of the light we create isn't even used by us to see.

When outdoor lighting influences an animal's (or a human's) perception of night, we call it "light pollution". Light pollution is relatively new to the environment, and we are still learning new things about its effect on wildlife.

Some things we do know about light pollution:

1. Wildlife and humans both experience negative health effects from light pollution. These changes include imbalanced hormones, disturbed sleep schedule, and feeding/foraging habit changes.
2. Light pollution, along with roads and other urban development can divide animal territories. This can trap animals where they shouldn't be or keep them from moving where they need to go.
3. Every year, millions of birds die by collision and predation in light polluted areas. Windows on buildings worsen the effect of local light pollution.

 

Organ Pipe Cactus is a great place to capture night sky photography.

NPS Photo/Derek Wallentinsen

Room for Improvement

Much of the light that we generate to see our surroundings at night is lost to the environment. Some of this is due to the density of light in an area, such as metropolitan centers. Some of this pollution is due to unchecked use of light in advertisements, billboards, and other untargeted lighting.

Some organizations bring awareness to light pollution and ways to mitigate its effects. The International Dark Sky Association provides more information on light pollution, as well as steps you can take to help create a darker night.

• Does the area need lighting? If you have lighting that does not serve a purpose, turn them off or remove the bulb.
• Is the light directed to where you need to see? Look at the light fixtures around your house. Is the light coming from them pointing to the sky? If so, consider changing the fixture so light is only shining on what you want to see.
• Are the lights brighter than you need? Some lights are unnecessarily bright, and put more light into the environment. Consider adding a dimmer switch or use a lower-wattage bulb.
• Do you leave your lights on all night? Consider using timers if you forget about lights, and motion sensors for security lights. This will save energy, money, and light pollution!

• What color lighting are you using? Lighting in outdoor spaces should be on the warmer end of the spectrum. Cooler, blue or white light contributes more light pollution. When you buy bulbs, look at the correlated color temperature (CCT) and make sure it’s 3000 K or lower.